GitLab: Deserialization of Untrusted Data
CVE-2026-87719 is a critical-severity deserialization of untrusted data vulnerability in GitLab, with a CVSS 3.1 base score of 9.9 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists versions 18.11.12, 19.0.9, 19.1.8 as the first without the flaw, so updating GitLab to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.57% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update GitLab to 18.11.12 or 19.0.9 or 19.1.8 or 19.2.6, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| GitLab | GitLab | 18.3 up to, but not including, 18.11.12; 19.0 up to, but not including, 19.0.9; 19.1 up to, but not including, 19.1.8; 19.2 up to, but not including, 19.2.6; 19.3 up to, but not including, 19.3.2 | 18.11.12, 19.0.9, 19.1.8, 19.2.6, 19.3.2 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H. Scored by CNA (gitlab.com).
Official description
GitLab has remediated an issue in GitLab EE affecting all versions from 18.3 before 18.11.12, 19.0 before 19.0.9, 19.1 before 19.1.8, 19.2 before 19.2.6, and 19.3 before 19.3.2 that under certain conditions could allow an authenticated user with Duo Chat access to obtain Advanced Search instance configurations and sensitive credentials using a specially crafted GraphQL subscription argument to bypass serialization and perform server object lookup.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Deserialization of Untrusted Data
The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.
How developers prevent this class of flaw
- If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.
- When deserializing data, populate a new object rather than just deserializing. The result is that the data flows through safe input validation and that the functions are safe.
- Explicitly define a final object() to prevent deserialization.
More Deserialization of Untrusted Data vulnerabilities (CWE-502)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
- hackerone.com/reports/4012289Permissions Required
Other vulnerabilities in GitLab
- 7.1 High severity
- 8.2 High severity
- 7.5 High severity
- 10.0 Critical severity
- 10.0 Critical severity
- 7.3 High severity
Recent Deserialization of Untrusted Data vulnerabilities
- 8.8 High severity
- 9.8 Critical severity
- 8.1 High severity
- 9.9 Critical severity
- 8.8 High severity
- 7.2 High severity
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