CVE-2021-3185Network attack vector

Code execution via unchecked H.264 marking index

Published Jan 25, 2021 · Updated Aug 3, 2024

Stack buffer overflow in GStreamer Bad Plug-ins before 1.18.1 allows remote attackers to execute code via crafted H.264 content. gst_h264_slice_parse_dec_ref_pic_marking increments n_ref_pic_marking without bounding writes to the ten-element ref_pic_marking stack array. Reachability requires an application to parse attacker-controlled H.264 through h264parse; exploitation can corrupt process memory, crash, or execute code.

CVSS severity9.8
Critical
EPSS probability2.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack buffer overflow in GStreamer Bad Plug-ins before 1.18.1 allows remote attackers to execute code via crafted H.264 content. gst_h264_slice_parse_dec_ref_pic_marking increments n_ref_pic_marking without bounding writes to the ten-element ref_pic_marking stack array. Reachability requires an application to parse attacker-controlled H.264 through h264parse; exploitation can corrupt process memory, crash, or execute code.

The record

CVE
CVE-2021-3185
Published
Jan 25, 2021
Updated
Aug 3, 2024
Vendor
Libslirp Project
Product
GStreamer Bad Plug-ins
Classifications
CWE-120, CWE-787, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 25, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Fixed in gst-plugins-bad-1.18.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Libslirp Project · GStreamer Bad Plug-insversion=Fixed in gst-plugins-bad-1.18.1

Published CVSS scores

7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
CWE-787Out-of-bounds Write
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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