Vulnerability-Lookup

RHSA-2026:98954

Vulnerability from csaf_redhat - Published: 2026-11-11 14:19 - Updated: 2026-11-11 19:13

Summary

Red Hat Security Advisory: mod_http2 security update

Severity

Important

Notes

Topic: An update for mod_http2 is now available for Red Hat Enterprise Linux 9.6 Extended Update Support. Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Details: The mod_h2 Apache httpd module implements the HTTP2 protocol (h2+h2c) on top of libnghttp2 for httpd 2.4 servers. Security Fix(es): * httpd: Apache HTTP Server: mod_http2 use-after-free / wild write via shared session->bbtmp re-entrancy (CVE-2026-57941) * httpd:2.4/mod_http2: mod_http2: httpd: Remote code execution in mod_http2 (CVE-2026-119618) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Terms of Use: This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Red Hat Inc. and provide a link to the original.

CVE-2026-57941

A flaw was found in the mod_http2 module of Apache HTTP Server. A remote, unauthenticated attacker could exploit a use-after-free condition—where memory is accessed after being released—through re-entrant processing of shared session buffers. This flaw can allow an attacker to potentially execute arbitrary code or crash the server, resulting in a Denial of Service (DoS).

7.0 (High)


                
                  CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H

CWE-416 - Use After Free

Affected products

Fixed 5 products

Product	Version	Remediation
Unresolved product id: AppStream-9.6.0.Z.EUS:mod_http2-0:2.0.26-4.el9_6.3.aarch64	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-9.6.0.Z.EUS:mod_http2-0:2.0.26-4.el9_6.3.ppc64le	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-9.6.0.Z.EUS:mod_http2-0:2.0.26-4.el9_6.3.s390x	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-9.6.0.Z.EUS:mod_http2-0:2.0.26-4.el9_6.3.src	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-9.6.0.Z.EUS:mod_http2-0:2.0.26-4.el9_6.3.x86_64	—	Vendor Fix fix Workaround

Known not affected 8 products

Product	Version	Remediation
Unresolved product id: AppStream-9.6.0.Z.EUS:mod_http2-debuginfo-0:2.0.26-4.el9_6.3.aarch64	—	Workaround
Unresolved product id: AppStream-9.6.0.Z.EUS:mod_http2-debuginfo-0:2.0.26-4.el9_6.3.ppc64le	—	Workaround
Unresolved product id: AppStream-9.6.0.Z.EUS:mod_http2-debuginfo-0:2.0.26-4.el9_6.3.s390x	—	Workaround
Unresolved product id: AppStream-9.6.0.Z.EUS:mod_http2-debuginfo-0:2.0.26-4.el9_6.3.x86_64	—	Workaround
Unresolved product id: AppStream-9.6.0.Z.EUS:mod_http2-debugsource-0:2.0.26-4.el9_6.3.aarch64	—	Workaround
Unresolved product id: AppStream-9.6.0.Z.EUS:mod_http2-debugsource-0:2.0.26-4.el9_6.3.ppc64le	—	Workaround
Unresolved product id: AppStream-9.6.0.Z.EUS:mod_http2-debugsource-0:2.0.26-4.el9_6.3.s390x	—	Workaround
Unresolved product id: AppStream-9.6.0.Z.EUS:mod_http2-debugsource-0:2.0.26-4.el9_6.3.x86_64	—	Workaround

Threats

Impact Moderate

CVE-2026-119618

A flaw was found in the mod_http2 module of the Apache HTTP Server (httpd), the standard web server used across Red Hat Enterprise Linux and other products. HTTP/2 allows a client to send many requests at the same time over a single connection, and the module handles these concurrent requests using multiple threads. Due to a thread-safety flaw, one thread can modify memory that belongs to another thread, corrupting the server's internal memory. A remote attacker who can reach the web server could exploit this flaw to execute arbitrary commands on the server without any authentication, potentially leading to a complete takeover of the affected system, unauthorized access to sensitive data, and service disruption. Only servers that have HTTP/2 enabled are affected; servers configured to serve only HTTP/1.1 are not vulnerable.

9.8 (Critical)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CWE-20 - Improper Input Validation

Affected products

Fixed 5 products, the same list as for CVE-2026-57941

Known not affected 8 products, the same list as for CVE-2026-57941

Threats

Impact Critical

References

15 references

URL	Category
https://access.redhat.com/errata/RHSA-2026:98954	self
https://access.redhat.com/security/updates/classi…	external
https://bugzilla.redhat.com/show_bug.cgi?id=2544864	external
https://bugzilla.redhat.com/show_bug.cgi?id=2567318	external
https://security.access.redhat.com/data/csaf/v2/a…	self
https://access.redhat.com/security/cve/CVE-2026-57941	self
https://bugzilla.redhat.com/show_bug.cgi?id=2544864	external
https://www.cve.org/CVERecord?id=CVE-2026-57941	external
https://nvd.nist.gov/vuln/detail/CVE-2026-57941	external
http://www.openwall.com/lists/oss-security/2026/1…	external
https://httpd.apache.org/security/vulnerabilities…	external
https://access.redhat.com/security/cve/CVE-2026-119618	self
https://bugzilla.redhat.com/show_bug.cgi?id=2567318	external
https://www.cve.org/CVERecord?id=CVE-2026-119618	external
https://nvd.nist.gov/vuln/detail/CVE-2026-119618	external

Acknowledgments

Google Cloud Vulnerability Research Simon Scannell Anthony Weems

JSON

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      "cwe": {
        "id": "CWE-416",
        "name": "Use After Free"
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      "discovery_date": "2026-10-01T23:10:33.829141+00:00",
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        {
          "category": "description",
          "text": "A flaw was found in the mod_http2 module of Apache HTTP Server. A remote, unauthenticated attacker could exploit a use-after-free condition\u2014where memory is accessed after being released\u2014through re-entrant processing of shared session buffers. This flaw can allow an attacker to potentially execute arbitrary code or crash the server, resulting in a Denial of Service (DoS).",
          "title": "Vulnerability description"
        },
        {
          "category": "summary",
          "text": "httpd: Apache HTTP Server: mod_http2 use-after-free / wild write via shared session-\u003ebbtmp re-entrancy",
          "title": "Vulnerability summary"
        },
        {
          "category": "other",
          "text": "A use-after-free flaw was found in mod_http2, the HTTP/2 module for the Apache HTTP Server. A remote attacker with no privileges can trigger re-entrant use of a shared per-session buffer (session-\u003ebbtmp) while the server is handling HTTP/2 traffic. That interleaving is not a single reliable request, and the demonstrated effect is a crash of the httpd worker, which is a denial of service. A further memory-corruption outcome has not been shown.",
          "title": "Statement"
        },
        {
          "category": "general",
          "text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product\u0027s status, and are included for informational purposes to better understand the severity of this vulnerability.",
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          "category": "external",
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          "details": "For details on how to apply this update, which includes the changes described in this advisory, refer to:\n\nhttps://access.redhat.com/articles/11258",
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          "details": "Moderate"
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      "title": "httpd: Apache HTTP Server: mod_http2 use-after-free / wild write via shared session-\u003ebbtmp re-entrancy"
    },
    {
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          "names": [
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        {
          "category": "description",
          "text": "A flaw was found in the mod_http2 module of the Apache HTTP Server (httpd), the standard web server used across Red Hat Enterprise Linux and other products. HTTP/2 allows a client to send many requests at the same time over a single connection, and the module handles these concurrent requests using multiple threads. Due to a thread-safety flaw, one thread can modify memory that belongs to another thread, corrupting the server\u0027s internal memory. A remote attacker who can reach the web server could exploit this flaw to execute arbitrary commands on the server without any authentication, potentially leading to a complete takeover of the affected system, unauthorized access to sensitive data, and service disruption. Only servers that have HTTP/2 enabled are affected; servers configured to serve only HTTP/1.1 are not vulnerable.",
          "title": "Vulnerability description"
        },
        {
          "category": "summary",
          "text": "httpd:2.4/mod_http2: mod_http2: httpd: Remote code execution in mod_http2",
          "title": "Vulnerability summary"
        },
        {
          "category": "other",
          "text": "The Red Hat Product Security team has assessed the severity of this vulnerability as Critical. It allows unauthenticated remote code execution, and public research has demonstrated a reliable exploit against a default-configured server with the mod_http2 module enabled. Successful exploitation allows an attacker to execute arbitrary commands, gain full control of the server process, and access or modify sensitive information.\n\nThe vulnerability\u0027s root cause is a thread-safety flaw in the mod_http2 module\u0027s handling of concurrent HTTP/2 requests: a worker thread writes into memory owned by the connection thread through a shared, lock-free allocator. This issue affects servers with HTTP/2 (h2 or h2c) enabled via the Protocols directive; servers serving only HTTP/1.1 are not affected.\n\nBecause exploitation depends on HTTP/2 stream workers sharing an allocator with the connection, the severity of this flaw varies across Red Hat products. The mod_http2 packages shipped in Red Hat Enterprise Linux 9 and Red Hat Enterprise Linux 10 allocate each HTTP/2 stream from a separate allocator, which substantially increases the complexity of exploiting the flaw. The severity for Red Hat Enterprise Linux 9 and Red Hat Enterprise Linux 10 is therefore rated Important rather than Critical. Versions of mod_http2 prior to 2.0.8 do not contain the affected code, and Red Hat Enterprise Linux 8 and earlier are not affected. Refer to the affected packages table for the severity assigned to each Red Hat product.",
          "title": "Statement"
        },
        {
          "category": "general",
          "text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product\u0027s status, and are included for informational purposes to better understand the severity of this vulnerability.",
          "title": "CVSS score applicability"
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            "AppStream-9.6.0.Z.EUS:mod_http2-0:2.0.26-4.el9_6.3.src",
            "AppStream-9.6.0.Z.EUS:mod_http2-0:2.0.26-4.el9_6.3.x86_64",
            "AppStream-9.6.0.Z.EUS:mod_http2-debuginfo-0:2.0.26-4.el9_6.3.aarch64",
            "AppStream-9.6.0.Z.EUS:mod_http2-debuginfo-0:2.0.26-4.el9_6.3.ppc64le",
            "AppStream-9.6.0.Z.EUS:mod_http2-debuginfo-0:2.0.26-4.el9_6.3.s390x",
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            "AppStream-9.6.0.Z.EUS:mod_http2-debugsource-0:2.0.26-4.el9_6.3.s390x",
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          ]
        }
      ],
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          "category": "impact",
          "details": "Critical"
        }
      ],
      "title": "httpd:2.4/mod_http2: mod_http2: httpd: Remote code execution in mod_http2"
    }
  ]
}

CVE-2026-119618 (GCVE-0-2026-119618)

Vulnerability from cvelistv5 – Published: 2026-11-11 14:54 – Updated: 2026-11-11 19:05

Title

Apache HTTP Server: mod_http2: heap corruption and RCE in assign_headers

Summary

Concurrent Execution using Shared Resource with Improper Synchronization vulnerability in Apache HTTP Server's mod_http2 in assign_headers() can lead to RCE. This issue affects Apache HTTP Server: from 2.4.55 through 2.4.70. Affected releases of mod_h2 from GitHub: from 2.0.8 through 2.0.42.

Severity

No CVSS data available.

CWE

CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization

Assigner

apache CNA under the mitre root

CNA scorecard B 76/100 over 1265 records in the last 180 days details

References

2 references

URL	Tags
https://httpd.apache.org/security/vulnerabilities…	vendor-advisory
http://www.openwall.com/lists/oss-security/2026/1…

Impacted products

1 product

Vendor	Product	Version
Apache Software Foundation	Apache HTTP Server	Affected: 2.4.55 , ≤ 2.4.70 (semver)

Credits

Anthropic's OSS Scanner, as vulnerability ANT-2026-MAPKT6MZ Anthony Weems and Simon Scannell of the Google Cloud Vulnerability Research

Show details on NVD website

JSON

To clipboard

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CVE-2026-57941 (GCVE-0-2026-57941)

Vulnerability from cvelistv5 – Published: 2026-10-01 16:06 – Updated: 2026-10-01 20:09

Title

Apache HTTP Server: mod_http2 use-after-free / wild write via shared session->bbtmp re-entrancy

Summary

Use After Free vulnerability in Apache HTTP Server's mod_http2 via shared session->bbtmp re-entrancy This issue affects Apache HTTP Server: from 2.4.0 through 2.4.68.

Severity

9.8 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

SSVC

Exploitation: none Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-01 19:06 UTC

CWE

CWE-416 - Use After Free

Assigner

apache CNA under the mitre root

CNA scorecard B 76/100 over 1265 records in the last 180 days details

References

2 references

URL	Tags
https://httpd.apache.org/security/vulnerabilities…	vendor-advisory
http://www.openwall.com/lists/oss-security/2026/1…

Impacted products

1 product

Vendor	Product	Version
Apache Software Foundation	Apache HTTP Server	Affected: 2.4.0 , ≤ 2.4.68 (semver)

Credits

Lucian Nitescu Simon Kappel Gianluca Danesin, Altervista

Show details on NVD website

JSON

To clipboard

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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

Order JSON

How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

Publication & reservation Sightings KEV catalogs Other timestamps

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

RHSA-2026:98954

CVE-2026-119618 (GCVE-0-2026-119618)

CVE-2026-57941 (GCVE-0-2026-57941)

Tags

Sightings

Nomenclature

Vulnerability timeline

Related by attack behaviour