Vulnerability-Lookup

GHSA-83X9-8WVQ-RRCP

Vulnerability from github – Published: 2026-07-18 15:31 – Updated: 2026-07-18 15:31

Details

The urwid web display backend (urwid/display/web.py) generates web session identifiers (urwid_id) in Screen.start() by concatenating two random.randrange(10**9) calls that use Python's Mersenne Twister PRNG, which is not cryptographically secure. Each call consumes approximately 30 bits of PRNG state, and the Mersenne Twister internal state is approximately 19,937 bits, so an attacker who observes approximately 334 session IDs (for example via the X-Urwid-ID HTTP response header) can fully reconstruct the internal state and predict all past and future session IDs (Path B). The same identifier is also used as the filename of a FIFO created in the world-listable /tmp directory (for example /tmp/urwid375487765176907690.in), so any local user on the host can list /tmp to enumerate active session tokens directly (Path A). With a valid session ID, an attacker can read the victim's terminal screen via the polling endpoint, inject keystrokes into the victim's session (yielding OS-level code execution with the session owner's privileges if the session runs a shell), and inject exit sequences or flood the FIFO to terminate or crash the session. A prior Bandit S311 warning on this usage was suppressed with # noqa: S311 rather than fixed

Severity

8.1 (High)


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

9.2 (Critical)


                  
                    CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

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{
  "affected": [],
  "aliases": [
    "CVE-2026-9323"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-338"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-18T14:17:12Z",
    "severity": "CRITICAL"
  },
  "details": "The urwid web display backend (urwid/display/web.py) generates web session identifiers (urwid_id) in Screen.start() by concatenating two random.randrange(10**9) calls that use Python\u0027s Mersenne Twister PRNG, which is not cryptographically secure. Each call consumes approximately 30 bits of PRNG state, and the Mersenne Twister internal state is approximately 19,937 bits, so an attacker who observes approximately 334 session IDs (for example via the X-Urwid-ID HTTP response header) can fully reconstruct the internal state and predict all past and future session IDs (Path B). The same identifier is also used as the filename of a FIFO created in the world-listable /tmp directory (for example /tmp/urwid375487765176907690.in), so any local user on the host can list /tmp to enumerate active session tokens directly (Path A). With a valid session ID, an attacker can read the victim\u0027s terminal screen via the polling endpoint, inject keystrokes into the victim\u0027s session (yielding OS-level code execution with the session owner\u0027s privileges if the session runs a shell), and inject exit sequences or flood the FIFO to terminate or crash the session. A prior Bandit S311 warning on this usage was suppressed with # noqa: S311 rather than fixed",
  "id": "GHSA-83x9-8wvq-rrcp",
  "modified": "2026-07-18T15:31:50Z",
  "published": "2026-07-18T15:31:50Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/urwid/urwid/security/advisories/GHSA-rjwp-g85x-gmjv"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-9323"
    },
    {
      "type": "WEB",
      "url": "https://github.com/urwid/urwid/issues/1127"
    },
    {
      "type": "WEB",
      "url": "https://github.com/urwid/urwid/pull/1128"
    },
    {
      "type": "WEB",
      "url": "https://github.com/urwid/urwid/commit/24acd12f0d0598036d0d577f2ee63e4a27b4a3d9"
    },
    {
      "type": "WEB",
      "url": "https://github.com/urwid/urwid"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/insecure-prng-and-information-exposure-in-urwid-web-display-backend"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ]
}

CVE-2026-9323 (GCVE-0-2026-9323)

Vulnerability from cvelistv5 – Published: 2026-07-18 13:51 – Updated: 2026-07-20 19:31

Title

Insecure PRNG and Information Exposure in urwid Web Display Backend

Summary

Severity

9.2 (Critical)


                        
                          CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

8.1 (High)


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

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator (v2.0.3)

CWE

CWE-338 - Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)

Assigner

VulnCheck

References

6 references

URL	Tags
https://github.com/urwid/urwid/security/advisorie…	vendor-advisory
https://github.com/urwid/urwid	product
https://github.com/urwid/urwid/commit/24acd12f0d0…	patch
https://github.com/urwid/urwid/issues/1127	issue-tracking
https://github.com/urwid/urwid/pull/1128	issue-tracking
https://www.vulncheck.com/advisories/insecure-prn…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version
urwid	urwid	Affected: 0 , ≤ 24acd12 (git)

Date Public

2026-07-18 00:00

Credits

Katriel Moses

Show details on NVD website

JSON

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                "id": "CVE-2026-9323",
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                  },
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                  }
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                "role": "CISA Coordinator",
                "timestamp": "2026-07-20T19:26:19.822918Z",
                "version": "2.0.3"
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          "vendor": "urwid",
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              "versionType": "git"
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      "credits": [
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      "datePublic": "2026-07-18T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "The urwid web display backend (urwid/display/web.py) generates web session identifiers (urwid_id) in Screen.start() by concatenating two random.randrange(10**9) calls that use Python\u0027s Mersenne Twister PRNG, which is not cryptographically secure. Each call consumes approximately 30 bits of PRNG state, and the Mersenne Twister internal state is approximately 19,937 bits, so an attacker who observes approximately 334 session IDs (for example via the X-Urwid-ID HTTP response header) can fully reconstruct the internal state and predict all past and future session IDs (Path B). The same identifier is also used as the filename of a FIFO created in the world-listable /tmp directory (for example /tmp/urwid375487765176907690.in), so any local user on the host can list /tmp to enumerate active session tokens directly (Path A). With a valid session ID, an attacker can read the victim\u0027s terminal screen via the polling endpoint, inject keystrokes into the victim\u0027s session (yielding OS-level code execution with the session owner\u0027s privileges if the session runs a shell), and inject exit sequences or flood the FIFO to terminate or crash the session. A prior Bandit S311 warning on this usage was suppressed with # noqa: S311 rather than fixed"
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      "metrics": [
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            "subConfidentialityImpact": "NONE",
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            "vulnerabilityResponseEffort": "NOT_DEFINED"
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    "datePublished": "2026-07-18T13:51:06.021Z",
    "dateReserved": "2026-05-22T20:56:42.239Z",
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    "state": "PUBLISHED"
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  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

Detection rules are retrieved from Rulezet.

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.

Action not permitted

GHSA-83X9-8WVQ-RRCP

CVE-2026-9323 (GCVE-0-2026-9323)

Tags

Sightings

Nomenclature