GHSA-gqr6-r77p-c2pj CVE-2026-55841
Fortigate syslog message parser can be exploited to modify or delete fields from the original message
- Severity
- 7.5 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 0.63%
- Chance of exploitation in the next 30 days. Higher than 50.36% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-138 Improper Neutralization of Special Elements
- Fix
6.3.12- Upgrade org.graylog2:graylog2-server to this version or later
Description
Impact
A security issue has been identified in Graylog affecting the parsing of syslog messages that use a key-value format, such as those generated by Fortigate devices.
The vulnerability allows attackers to overwrite individual message fields, or to produce invalid messages which Graylog will discard. This effectively enables log evasion techniques to obscure malicious activity.
Patches
The issue has been fixed in the following Graylog versions: 6.3.12, 7.0.7, 7.1.2. Users should upgrade to one of these versions or above to remediate the vulnerability.
Graylog Cloud has already been patched.
Workarounds
There are no feasible workarounds for this issue. Upgrading to a patched version is recommended.
To find potentially discarded messages due to parsing errors, customers of Graylog Enterprise or Security can check the Indexing and Processing Failures Index^1.
Credits
Thanks to Jose Luis González, from Fundación Sarenet, with additional analysis by Borja Marcos from Sarenet.
Affected versions
Maven
| Package | Vulnerable | Fixed in |
|---|---|---|
| org.graylog2:graylog2-server | < 6.3.12 |
6.3.12 |
| org.graylog2:graylog2-server | >= 7.0.0, < 7.0.7 |
7.0.7 |
| org.graylog2:graylog2-server | >= 7.1.0, < 7.1.2 |
7.1.2 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
org.graylog2:graylog2-server Maven → 6.3.12
- maven
<dependency><groupId>org.graylog2</groupId><artifactId>graylog2-server</artifactId><version>6.3.12</version></dependency>- gradle
implementation("org.graylog2:graylog2-server:6.3.12")
Severity breakdown
CVSS 3.1 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
Weakness
CWE-138: Improper Neutralization of Special Elements
The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as control elements or syntactic markers when they are sent to a downstream component.
How to prevent it
- Implementation: Developers should anticipate that special elements (e.g. delimiters, symbols) will be injected into input vectors of their product. One defense is to create an allowlist (e.g. a regular expression) that defines valid input according to the requirements specifications. Strictly filter any input that does not match against the allowlist. Properly encode your output, and quote any elements that have special meaning to the component with which you are communicating.
- Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- Implementation: Use and specify an appropriate output encoding to ensure that the special elements are well-defined. A normal byte sequence in one encoding could be a special element in another.
- Implementation: Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
- Implementation: While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments. The most conservative approach is to escape or filter all characters that do not pass an extremely strict allowlist (such as everything that is not alphanumeric or white space). If some special characters are still needed, such as white space, wrap each argument in quotes after the escaping/filtering step. Be careful of argument injection (CWE-88).
References
Packages
Other links
- github.com/Graylog2/graylog2-server/security/advisories/GHSA-gqr6-r77p-c2pj
- github.com/Graylog2/graylog2-server/pull/26050
- github.com/Graylog2/graylog2-server/pull/26056
- github.com/Graylog2/graylog2-server/pull/26057
- github.com/Graylog2/graylog2-server/pull/26059
- github.com/Graylog2/graylog2-server/commit/793df6e8202ea55c15a762e47a2a8a775961…
- github.com/Graylog2/graylog2-server/commit/85dc699d6319aea433583dc239077a3a799c…
- github.com/Graylog2/graylog2-server/commit/d5051e604c962ef3d4e5e8e434d0ff4907d2…
- github.com/Graylog2/graylog2-server/commit/dde76d7432c469887d9a95c208083c5f0f73…
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-m9c2-85gv-8xr5 Graylog: Manager-to-Owner privilege escalation on saved searches and dashboards | Medium | Also affects org.graylog2:graylog2-server |
| GHSA-j769-9gv9-65gr Graylog token revocation endpoint allows authenticated users to delete other users’ access tokens | Medium | Also affects org.graylog2:graylog2-server |
| GHSA-q79r-r9xg-r863 Graylog Server: System Catalog titles endpoint can be used to retrieve values of protected database fields | Medium | Also affects org.graylog2:graylog2-server |
| GHSA-3m86-c9x3-vwm9 Graylog vulnerable to privilege escalation through API tokens | High | Also affects org.graylog2:graylog2-server |
| GHSA-76vf-mpmx-777j Graylog Allows Session Takeover via Insufficient HTML Sanitization | Medium | Also affects org.graylog2:graylog2-server |
| GHSA-q9q2-3ppx-mwqf Graylog Allows Stored Cross-Site Scripting via Files Plugin and API Browser | High | Also affects org.graylog2:graylog2-server |
| GHSA-q7g5-jq6p-6wvx Graylog's Authenticated HTTP inputs ingest message even if Authorization header is missing or has wrong value | Medium | Also affects org.graylog2:graylog2-server |
| GHSA-p6gg-5hf4-4rgj Graylog vulnerable to instantiation of arbitrary classes triggered by API request | High | Also affects org.graylog2:graylog2-server |
MergeHarbor checks every repository's dependencies against this database, ranks what matters by exploitability and reachability, routes it to the owning team and opens the fix pull request.
Check your repos with MergeHarbor