FreeType Out-of-Bounds Write Vulnerability
FreeType · FreeType
FreeType versions 2.13.0 and below contain an out-of-bounds write in the font parsing code that handles subglyph structures for TrueType GX and variable font files. An attacker who can supply a crafted font file to a vulnerable FreeType build could trigger a heap buffer that is too small and write out of bounds, potentially achieving arbitrary code execution; the attack is network-reachable with no authentication or user interaction required, though exploitation is considered high complexity.
An out of bounds write exists in FreeType versions 2.13.0 and below (newer versions of FreeType are not vulnerable) when attempting to parse font subglyph structures related to TrueType GX and variable font files. The vulnerable code assigns a signed short value to an unsigned long and then adds a static value causing it to wrap around and allocate too small of a heap buffer. The code then writes up to 6 signed long integers out of bounds relative to this buffer. This may result in arbitrary code execution. This vulnerability may have been exploited in the wild.
- Exploited
- Yes, in CISA KEV
- Reports
- 0
- Tactics
- 3/15
How an attack unfolds
Based on MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. mappings. Select a step to see the evidence.Exploitation timelineDated milestones for a CVE: when it was disclosed, when exploit code became public, when exploitation was confirmed, and when threat reports named it.
First seen exploited the day it was disclosed. Public exploit code (PoC-in-GitHub) appeared 12 days after disclosure.
- Public exploit codePoC-in-GitHub+12 days
- Added to CISA KEVEU database agrees+56 days
CISA KEV listing is when exploitation was confirmed, not necessarily the first attack.
MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. techniques
2 TechniqueOne specific attacker behaviour in MITRE ATT&CK, such as T1190 “Exploit Public-Facing Application”. IDs with a dot, like T1059.004, are sub-techniques., grouped by TacticThe attacker’s goal at a stage of an attack in MITRE ATT&CK, such as Initial Access or Persistence. Each technique belongs to one or more tactics. in kill-chain order 2ExecutionTA0002
Out of bounds write exists in FreeType that has been exploited through malicious font files, causing the application to crash.
ImpactTA0040
Lower-confidence links (1)
These come from early or generic mappings, text matching, or contradict this CVE’s details (for example a public-facing technique on a bug that needs a user to open a file). Shown for completeness.
- Malicious FileT1204.002 server-side bug exploitable without user interaction; client-execution technique does not fit
Detection
0 rules for this CVE · 11 general rules for its techniquesRules for this CVE
0Sigma ruleAn open, vendor-neutral detection rule for log data. Security teams convert Sigma rules into searches for their own SIEM. that reference CVE-2025-27363 directly.CVE-specific rules are not available in this build. Search SigmaHQ ↗
General rules for this CVE’s techniques
These detect the technique in general, not this specific vulnerability.
Hijack Execution FlowT15748 general rules
- Exploiting SetupComplete.cmd CVE-2019-1378hightest
- Potential PrintNightmare Exploitation Attempthightest
- Suspicious Printer Driver Empty Manufacturerhightest
- DLL Execution Via Register-cimprovider.exemediumtest
- Potential Initial Access via DLL Search Order Hijackingmediumtest
- Potential Registry Persistence Attempt Via DbgManagedDebuggermediumtest
- Regsvr32 DLL Execution With Uncommon Extensionmediumtest
- Windows Spooler Service Suspicious Binary Loadinformationaltest
Application or System ExploitationT1499.0043 general rules
- Audit CVE Eventcriticaltest
- Apache Segmentation Faulthightest
- Nginx Core Dumphightest
Sigma rules © SigmaHQ, Detection Rule License 1.1; linked, not reproduced.
What security researchers reported
Not named in any threat report yetAlso mentioned in 50 community threat pulses (AlienVault OTX)
Weaker evidencePulses are indicator collections that anyone can publish. A mention is not confirmation of exploitation.
- Actively_Exploited_Kev | Oct 30, 202629 Oct 2026
- Actively_Exploited_Kev | Oct 29, 202628 Oct 2026
- Actively_Exploited_Kev | Oct 28, 202627 Oct 2026
- Actively_Exploited_Kev | Oct 27, 202626 Oct 2026
- Actively_Exploited_Kev | Oct 24, 202623 Oct 2026
- Actively_Exploited_Kev | Oct 23, 202622 Oct 2026
- 44 more on OTX