CVE-2026-21918 (GCVE-0-2026-21918)
Vulnerability from cvelistv5 – Published: 2026-01-15 20:27 – Updated: 2026-01-15 21:13
VLAI
EPSS
VEX
Title
Junos OS: SRX and MX Series: When TCP packets occur in a specific sequence flowd crashes
Summary
A Double Free vulnerability in the flow processing daemon (flowd) of Juniper Networks Junos OS on SRX and MX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). On all SRX and MX Series platforms, when during TCP session establishment a specific sequence of packets is encountered a double free happens. This causes flowd to crash and the respective FPC to restart.
This issue affects Junos OS on SRX and MX Series:
* all versions before 22.4R3-S7,
* 23.2 versions before 23.2R2-S3,
* 23.4 versions before 23.4R2-S4,
* 24.2 versions before 24.2R2.
Severity
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-01-15 21:12 UTC
CWE
- CWE-415 - Double Free
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://supportportal.juniper.net/JSA106018 | vendor-advisory |
| https://kb.juniper.net/JSA106018 | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Juniper Networks | Junos OS |
Affected:
0 , < 22.4R3-S7
(semver)
Affected: 23.2 , < 23.2R2-S3 (semver) Affected: 23.4 , < 23.4R2-S4 (semver) Affected: 24.2 , < 24.2R2 (semver) |
guessed |
Date Public
2026-01-14 17:00
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
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.
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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.
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.
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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.
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