VulnerabilityPublished 13 Aug 2026

CVE-2026-73557: vllm · Race Condition

Affects vllmSource CVE Database V5

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Mentioned vulnerabilities

CVE-2025-62164

Not known to be exploited · CVSS 6.3 Medium : upgrade to 0.26.0 when convenient.

Data as of 12 Nov 2026, 23:24 UTC

CVSS 4.0 base score

6.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 16% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.26.0

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

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: Present
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade vllm to 0.26.0.

Affected software

Product	Affected	Fixed in
vllm-projectvllm	Affected >=0.20.2rc0 <0.26.0	Fixed in 0.26.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, avoid enabling the --enable-prompt-embeds feature in production environments. If this feature is required, consider applying additional synchronization controls or isolating usage to trusted inputs.

Description

CVE-2026-73557 is a race condition vulnerability in the vllm-project's vllm software affecting versions from 0.20.2rc0 up to but not including 0.26.0. It arises from improper synchronization of a process-global sparse tensor invariant guard in PyTorch 2.11.0 during concurrent prompt-embedding reconstruction within a single chat completion request. This can lead to invalid sparse tensor deserialization and subsequent unsafe dense tensor conversion. The vulnerability requires the --enable-prompt-embeds feature (default off) but does not require multiple workers or multimodal embeddings. The flaw allows a malicious payload to bypass the follow-up guard, potentially causing memory corruption or denial of service as documented in the related CVE-2025-62164. The CVSS 4.0 base score is 6.3 (medium severity).

Impact

An attacker can bypass the sparse tensor invariant guard due to a race condition, causing deserialization of malformed sparse tensors. This can lead to memory corruption, denial of service, or potentially code execution as previously documented for CVE-2025-62164. The concurrency flaw allows a malicious payload to be processed unsafely within a single chat completion request, increasing the risk of exploitation. However, the --enable-prompt-embeds feature is default off, reducing exposure unless explicitly enabled. API authentication is optional, so unauthenticated requests may trigger the vulnerability if the feature is enabled.

Summary

This vulnerability is a concurrency issue (CWE-362) in vllm versions >=0.20.2rc0 <0.26.0 where the process-global sparse tensor invariant guard used in torch.sparse.check_sparse_tensor_invariants() is improperly synchronized. The guard uses save/enable/restore operations on a global flag in PyTorch 2.11.0. When two prompt-embedding parts are processed concurrently in one /v1/chat/completions request, one context may restore the global flag to false while the other is still inside its guarded section. This allows the second context to load an invalid sparse tensor without the invariant check, leading to unsafe tensor.to_dense() calls. The vulnerability builds on the previously reported CVE-2025-62164 but introduces a distinct concurrency root cause. Exploitation requires the --enable-prompt-embeds flag but not other optional features. The vulnerability was introduced after partial fixes for CVE-2025-62164 and is confirmed by deterministic testing with hash-verified source. The affected code is in vllm/renderers/embed_utils.py around the guarded loader. The vulnerability does not require API authentication and can be triggered in the default server configuration if --enable-prompt-embeds is enabled.

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition) (opens in a new tab)
Class weaknessLikelihood of exploit: MediumOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
Architecture and Design
In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
Architecture and Design
Use thread-safe capabilities such as the data access abstraction in Spring.
Architecture and Design
Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V1.11.2 (opens in a new tab)
Attack patterns
Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions (opens in a new tab)
Leveraging Race Conditions (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 13 Sep 2026, 13:03 UTC

WeaknessesCWE-362

Technical details

References

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