CVE-2026-50256 (GCVE-0-2026-50256)

Vulnerability from cvelistv5 – Published: 2026-06-05 10:31 – Updated: 2026-06-25 13:16
VLAI
Title
Xorg-x11-server: xorg-x11-server-xwayland: xorg-x11-server: stack buffer overflow in font alias resolution due to libxfont2 name length mismatch
Summary
A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. A mismatch between the X server and the libXfont2 library's maximum font name length can cause a stack buffer overflow during font alias resolution. The server allocates a 256 byte stack buffer but libXfont2's alias target name length is 1024 bytes. A font alias name between 257 and 1023 bytes causes the X server to copy that name into the undersized stack buffer without further checks. This may be used to crash the server, or for privilege escalation if the X server runs as root.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
  • CWE-121 - Stack-based Buffer Overflow
Assigner
References
Impacted products
Vendor Product Version
Red Hat Red Hat Enterprise Linux 10 Unaffected: 0:24.1.9-4.el10_2.2 , < * (rpm)
    cpe:/o:redhat:enterprise_linux:10.2
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Red Hat Red Hat Enterprise Linux 8 Unaffected: 0:21.1.3-20.el8_10.2 , < * (rpm)
    cpe:/a:redhat:enterprise_linux:8::appstream
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Red Hat Red Hat Enterprise Linux 8 Unaffected: 0:1.20.11-28.el8_10.2 , < * (rpm)
    cpe:/a:redhat:enterprise_linux:8::appstream
    cpe:/a:redhat:enterprise_linux:8::crb
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Red Hat Red Hat Enterprise Linux 8 Unaffected: 0:1.15.0-10.el8_10 , < * (rpm)
    cpe:/a:redhat:enterprise_linux:8::appstream
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Red Hat Red Hat Enterprise Linux 9 Unaffected: 0:24.1.9-4.el9_8.2 , < * (rpm)
    cpe:/a:redhat:enterprise_linux:9::appstream
    cpe:/a:redhat:enterprise_linux:9::crb
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Red Hat Red Hat Enterprise Linux 9 Unaffected: 0:1.20.11-34.el9_8.2 , < * (rpm)
    cpe:/a:redhat:enterprise_linux:9::appstream
    cpe:/a:redhat:enterprise_linux:9::crb
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Red Hat Red Hat Enterprise Linux 9 Unaffected: 0:1.15.0-7.el9_8.2 , < * (rpm)
    cpe:/a:redhat:enterprise_linux:9::appstream
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Red Hat Red Hat Enterprise Linux 6     cpe:/o:redhat:enterprise_linux:6
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Red Hat Red Hat Enterprise Linux 7     cpe:/o:redhat:enterprise_linux:7
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Date Public
2026-06-02 00:00
Credits
Upstream acknowledges Anonymous (Trend Micro Zero Day Initiative) as the original reporter.
Show details on NVD website
To clipboard 

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\"packageName\": \"xorg-x11-server\", \"collectionURL\": \"https://access.redhat.com/downloads/content/package-browser/\", \"defaultStatus\": \"unknown\"}, {\"cpes\": [\"cpe:/o:redhat:enterprise_linux:7\"], \"vendor\": \"Red Hat\", \"product\": \"Red Hat Enterprise Linux 7\", \"packageName\": \"tigervnc\", \"collectionURL\": \"https://access.redhat.com/downloads/content/package-browser/\", \"defaultStatus\": \"affected\"}, {\"cpes\": [\"cpe:/o:redhat:enterprise_linux:7\"], \"vendor\": \"Red Hat\", \"product\": \"Red Hat Enterprise Linux 7\", \"packageName\": \"xorg-x11-server\", \"collectionURL\": \"https://access.redhat.com/downloads/content/package-browser/\", \"defaultStatus\": \"affected\"}], \"timeline\": [{\"lang\": \"en\", \"time\": \"2026-05-15T03:14:46.000Z\", \"value\": \"Reported to Red Hat.\"}, {\"lang\": \"en\", \"time\": \"2026-06-02T00:00:00.000Z\", \"value\": \"Made public.\"}], \"datePublic\": \"2026-06-02T00:00:00.000Z\", \"references\": [{\"url\": \"https://access.redhat.com/errata/RHSA-2026:26562\", \"name\": \"RHSA-2026:26562\", \"tags\": [\"vendor-advisory\", \"x_refsource_REDHAT\"]}, {\"url\": \"https://access.redhat.com/errata/RHSA-2026:26566\", \"name\": \"RHSA-2026:26566\", \"tags\": [\"vendor-advisory\", \"x_refsource_REDHAT\"]}, {\"url\": \"https://access.redhat.com/errata/RHSA-2026:26590\", \"name\": \"RHSA-2026:26590\", \"tags\": [\"vendor-advisory\", \"x_refsource_REDHAT\"]}, {\"url\": \"https://access.redhat.com/errata/RHSA-2026:26610\", \"name\": \"RHSA-2026:26610\", \"tags\": [\"vendor-advisory\", \"x_refsource_REDHAT\"]}, {\"url\": \"https://access.redhat.com/errata/RHSA-2026:26709\", \"name\": \"RHSA-2026:26709\", \"tags\": [\"vendor-advisory\", \"x_refsource_REDHAT\"]}, {\"url\": \"https://access.redhat.com/errata/RHSA-2026:28923\", \"name\": \"RHSA-2026:28923\", \"tags\": [\"vendor-advisory\", \"x_refsource_REDHAT\"]}, {\"url\": \"https://access.redhat.com/errata/RHSA-2026:29844\", \"name\": \"RHSA-2026:29844\", \"tags\": [\"vendor-advisory\", \"x_refsource_REDHAT\"]}, {\"url\": \"https://access.redhat.com/security/cve/CVE-2026-50256\", \"tags\": [\"vdb-entry\", \"x_refsource_REDHAT\"]}, {\"url\": \"https://bugzilla.redhat.com/show_bug.cgi?id=2485380\", \"name\": \"RHBZ#2485380\", \"tags\": [\"issue-tracking\", \"x_refsource_REDHAT\"]}, {\"url\": \"https://gitlab.freedesktop.org/xorg/xserver/-/commit/bb5158f962dc935e58ef8b4b5fcb31be201a6e07\"}, {\"url\": \"https://lists.x.org/archives/xorg-announce/2026-June/003702.html\"}, {\"url\": \"https://redhat.atlassian.net/browse/PSIRTSUPT-16950\"}], \"x_generator\": {\"engine\": \"cvelib 1.8.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. A mismatch between the X server and the libXfont2 library\u0027s maximum font name length can cause a stack buffer overflow during font alias resolution. The server allocates a 256 byte stack buffer but libXfont2\u0027s alias target name length is 1024 bytes. A font alias name between 257 and 1023 bytes causes the X server to copy that name into the undersized stack buffer without further checks. This may be used to crash the server, or for privilege escalation if the X server runs as root.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-121\", \"description\": \"Stack-based Buffer Overflow\"}]}], \"providerMetadata\": {\"orgId\": \"53f830b8-0a3f-465b-8143-3b8a9948e749\", \"shortName\": \"redhat\", \"dateUpdated\": \"2026-06-25T13:16:04.915Z\"}, \"x_redhatCweChain\": \"CWE-121: Stack-based Buffer Overflow\"}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-50256\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-06-25T13:16:04.915Z\", \"dateReserved\": \"2026-06-04T14:55:24.011Z\", \"assignerOrgId\": \"53f830b8-0a3f-465b-8143-3b8a9948e749\", \"datePublished\": \"2026-06-05T10:31:22.122Z\", \"assignerShortName\": \"redhat\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.