Evidence used
- No CISA KEV confirmation is currently recorded.
- EPSS is 0.19% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2026
CVE-2026-63276High confidence
Stack buffer overflow in CFF to Type 1 font conversion
The Document Foundation · LibreOffice
5.4MediumCVSS 4.0
Patch only the product branches with a verified fix
Fix availability varies by productMedium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 671 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityMedium→Operational priority:Medium, unchanged from published severity.unchanged
Compensating controls
- Apply the linked authoritative mitigation while planning the permanent fix.
- Restrict local access and enforce least privilege on affected hosts.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs The Document Foundation LibreOffice and falls inside the recorded affected range.
- Recheck the vendor advisory before scheduling a change because no verified fixed version is currently retained.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Remediation availability differs by product scope
Verified remediation exists for at least one product or source, but 671 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
- Red Hat Product Security: 670 affected or under-investigation product states without a fixed product state in the same current advisory
- Debian Security Tracker: 1 affected package state with no published fix
Distribution package intelligence
5 package statesRelease-specific package status
Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.
Package result overrides the generic status
BlackTree has verified remediation for at least one product or source, but the relevant distribution still reports no fixed package for 1 affected package state shown here. Treat those rows as affected with no fix until that distribution publishes a fixed version.
Repository candidate not checked
A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.
| Distribution release | Source package | Vendor state | Fixed version | Evidence |
|---|---|---|---|---|
| Debian trixietrixie · source | libreoffice | Vendor fix publishedDebian records a fixed source-package version for this release. | 4:25.2.3-2+deb13u7 | Debian Security Tracker ↗Source updated 7 Oct 2026 |
| Debian bookwormbookworm · source | libreoffice | Affected, no fix publishedDebian currently tracks this release as open. | Not published in this feed | Debian Security Tracker ↗Source updated 7 Oct 2026 |
| Debian forkyforky · source | libreoffice | Vendor fix publishedDebian records a fixed source-package version for this release. | 4:26.2.5.2-1 | Debian Security Tracker ↗Source updated 7 Oct 2026 |
| Debian sidsid · source | libreoffice | Vendor fix publishedDebian records a fixed source-package version for this release. | 4:26.2.5.2-1 | Debian Security Tracker ↗Source updated 7 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | libreoffice | Vendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree. | 4:24.2.7-0ubuntu0.24.04.7 | Canonical Ubuntu Security ↗Source updated 7 Oct 2026 |
Direct vendor intelligence
1 currentAuthoritative vendor CSAF and VEX advisories
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
CVE-2026-63276 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitylibreoffice: stack buffer overflow in CFF to Type 1 font conversion
The vendor explicitly identifies these products as affected by this CVE.
- autocorr-af as a component of Red Hat Enterprise Linux 6
- autocorr-bg as a component of Red Hat Enterprise Linux 6
- autocorr-ca as a component of Red Hat Enterprise Linux 6
- autocorr-cs as a component of Red Hat Enterprise Linux 6
- autocorr-da as a component of Red Hat Enterprise Linux 6
- autocorr-de as a component of Red Hat Enterprise Linux 6
- autocorr-en as a component of Red Hat Enterprise Linux 6
- autocorr-es as a component of Red Hat Enterprise Linux 6
- autocorr-eu as a component of Red Hat Enterprise Linux 6
- autocorr-fa as a component of Red Hat Enterprise Linux 6
- autocorr-fi as a component of Red Hat Enterprise Linux 6
- autocorr-fr as a component of Red Hat Enterprise Linux 6
- Summary
- A flaw was found in LibreOffice. When a user exports a document with crafted embedded fonts to PDF, a stack-based buffer overflow can occur during the conversion of CFF fonts to Type 1 fonts due to improper bounds checking. This issue can cause memory corruption, resulting in an application crash.
- Remediation
- Do not export documents from unknown or untrusted sources to PDF with LibreOffice.
Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 671 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
Fix availability varies by product01
What, why and how
LibreOffice converts CFF fonts to Type 1 when it subsets a font, which happens when a document is exported to PDF, and CFF fonts may be embedded in documents. A stack buffer overflow existed in that conversion. The converted operators were written into a fixed size buffer with no check that they still fit, so a glyph emitting many operators wrote past the end of the buffer. In fixed versions the remaining capacity is tracked and the conversion stops when it is used up.
What
LibreOffice converts CFF fonts to Type 1 when it subsets a font, which happens when a document is exported to PDF, and CFF fonts may be embedded in documents. A stack buffer overflow existed in that conversion. The converted operators were written into a fixed size buffer with no check that they still fit, so a glyph emitting many operators wrote past the end of the buffer. In fixed versions the remaining capacity is tracked and the conversion stops when it is used up.
Why
A bounds error lets data be written beyond the intended memory region, potentially corrupting control data.
How
An attacker operating through local access may attempt exploitation when the stated preconditions are met. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
LibreOffice converts CFF fonts to Type 1 when it subsets a font, which happens when a document is exported to PDF, and CFF fonts may be embedded in documents. A stack buffer overflow existed in that conversion. The converted operators were written into a fixed size buffer with no check that they still fit, so a glyph emitting many operators wrote past the end of the buffer. In fixed versions the remaining capacity is tracked and the conversion stops when it is used up.
Why
A bounds error lets data be written beyond the intended memory region, potentially corrupting control data.
How
An attacker operating through local access may attempt exploitation when the stated preconditions are met. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- local access → Out-of-bounds Write → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Local
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- Passive interaction required
- Attack complexity
- Low: no specialised conditions are recorded
- Security boundary
- Not a CVSS 4.0 base metric
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-787 ↗
CWE-787: Out-of-bounds Write. The product writes data past the end, or before the beginning, of the intended buffer.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N/E:PCommon Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.
AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATNoneAttack requirements: No additional deployment or execution condition is required.PRNonePrivileges required: The attacker does not need an account or existing privileges.UIPassiveUser interaction: A user must unknowingly interact with the vulnerable system.VCLowVulnerable-system confidentiality: A successful attack can cause a limited loss.VILowVulnerable-system integrity: A successful attack can cause a limited loss.VAHighVulnerable-system availability: A successful attack can cause a major loss.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.- Post-exploitation / living off the land
- The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Fix availability varies by product
- Affected
- autocorr-af as a component of Red Hat Enterprise Linux 6
- autocorr-bg as a component of Red Hat Enterprise Linux 6
- autocorr-ca as a component of Red Hat Enterprise Linux 6
- autocorr-cs as a component of Red Hat Enterprise Linux 6
- autocorr-da as a component of Red Hat Enterprise Linux 6
- autocorr-de as a component of Red Hat Enterprise Linux 6
- autocorr-en as a component of Red Hat Enterprise Linux 6
- autocorr-es as a component of Red Hat Enterprise Linux 6
- autocorr-eu as a component of Red Hat Enterprise Linux 6
- autocorr-fa as a component of Red Hat Enterprise Linux 6
- autocorr-fi as a component of Red Hat Enterprise Linux 6
- autocorr-fr as a component of Red Hat Enterprise Linux 6
- autocorr-ga as a component of Red Hat Enterprise Linux 6
- autocorr-hr as a component of Red Hat Enterprise Linux 6
- autocorr-hu as a component of Red Hat Enterprise Linux 6
- autocorr-is as a component of Red Hat Enterprise Linux 6
- autocorr-it as a component of Red Hat Enterprise Linux 6
- autocorr-ja as a component of Red Hat Enterprise Linux 6
- autocorr-ko as a component of Red Hat Enterprise Linux 6
- autocorr-lb as a component of Red Hat Enterprise Linux 6
- autocorr-lt as a component of Red Hat Enterprise Linux 6
- autocorr-mn as a component of Red Hat Enterprise Linux 6
- autocorr-nl as a component of Red Hat Enterprise Linux 6
- autocorr-pl as a component of Red Hat Enterprise Linux 6
- autocorr-pt as a component of Red Hat Enterprise Linux 6
- autocorr-ro as a component of Red Hat Enterprise Linux 6
- autocorr-ru as a component of Red Hat Enterprise Linux 6
- autocorr-sk as a component of Red Hat Enterprise Linux 6
- autocorr-sl as a component of Red Hat Enterprise Linux 6
- autocorr-sr as a component of Red Hat Enterprise Linux 6
- and 640 more
- Action
- Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
- Workaround
- Do not export documents from unknown or untrusted sources to PDF with LibreOffice.
04
Evidence and provenance
Published 22 Sept 2026 · Last source change 22 Sept 2026, 12:21 UTC · CWE-787 · Out-of-bounds Write
CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source FIRST · tracked since 2026-09-23
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2026-84356
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD not scheduled
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- Vendor guidanceAuthoritative vendor guidance changed from remediation: access.redhat.com/CVE-2026-63276 to remediation: access.redhat.com/CVE-2026-63276.Red Hat Product Security ↗
- Before
- remediation: access.redhat.com/CVE-2026-63276
- After
- remediation: access.redhat.com/CVE-2026-63276
- Remediation statusRemediation status changed from Awaiting fix to Mitigation available.Red Hat Product Security ↗
- Before
- Awaiting fix
- After
- Mitigation available
- Affected versionsThe structured affected or fixed version information changed.Red Hat Product Security ↗
- Before
- After
- autocorr-af as a component of Red Hat Enterprise Linux 6; autocorr-bg as a component of Red Hat Enterprise Linux 6; autocorr-ca as a component of Red Hat Enterprise Linux 6; autocorr-cs as a component of Red Hat Enterprise Linux 6; autocorr-da as a component of Red Hat Enterprise Linux 6; autocorr-de as a component of Red Hat Enterprise Linux 6; autocorr-en as a component of Red Hat Enterprise Linux 6; autocorr-es as a component of Red Hat Enterprise Linux 6; autocorr-eu as a component of Red Hat Enterprise Linux 6; autocorr-fa as a component of Red Hat Enterprise Linux 6; autocorr-fi as a component of Red Hat Enterprise Linux 6; autocorr-fr as a component of Red Hat Enterprise Linux 6; autocorr-ga as a component of Red Hat Enterprise Linux 6; autocorr-hr as a component of Red Hat Enterprise Linux 6; autocorr-hu as a component of Red Hat Enterprise Linux 6; autocorr-is as a component of Red Hat Enterprise Linux 6; autocorr-it as a component of Red Hat Enterprise Linux 6; autocorr-ja as a component of Red Hat Enterprise Linux 6; autocorr-ko as a component of Red Hat Enterprise Linux 6; autocorr-lb as a component of Red Hat Enterprise Linux 6; autocorr-lt as a component of Red Hat Enterprise Linux 6; autocorr-mn as a component of Red Hat Enterprise Linux 6; autocorr-nl as a component of Red Hat Enterprise Linux 6; autocorr-pl as a component of Red Hat Enterprise Linux 6; autocorr-pt as a component of Red Hat Enterprise Linux 6; autocorr-ro as a component of Red Hat Enterprise Linux 6; autocorr-ru as a component of Red Hat Enterprise Linux 6; autocorr-sk as a component of Red Hat Enterprise Linux 6; autocorr-sl as a component of Red Hat Enterprise Linux 6; autocorr-sr as a component of Red Hat Enterprise Linux 6; and 640 more
- ENISA EUVD mappingEUVD-2026-84356 was added to the official ENISA EUVD mapping for this CVE.ENISA EUVD ↗
- Before
- not recorded
- After
- {"euvdId":"EUVD-2026-84356"}
- Catalogue recordCVE added to the BlackTree catalogue.CNA ↗
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.