Gdb: gdbserver: heap buffer overflow in cmd_qtdpsrc via qtdpsrc declared/actual length mismatch
Affects gdbserver as shipped with Red Hat Enterprise Linux 6 through 10 and Red Hat Hardened Images, when its port is reachable over the network. CVSS scores it 8.1 (high). No fix is listed in the checked facts.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- No fix listed
- Who is exposed
- Not reported
Do first: Workaround: Limit network access to the gdbserver port, for example with a firewall rule, because exposure is limited only by network access to that port. Stop gdbserver when it is not needed.
- Last modified
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 41/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Unclear
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: no
- Technical impact: total
Summary
A heap buffer overflow in the gdbserver component of GDB lets a remote attacker, without logging in, run native code inside the gdbserver process. The flaw is triggered by a crafted QTDPsrc packet whose declared source length does not match the actual data length, causing data to be written past the end of a heap buffer.
Read the original description
A heap buffer overflow in gdbserver's QTDPsrc packet handler allows an unauthenticated remote attacker to achieve native code execution in the gdbserver process. The vulnerability results from a mismatch between a packet's declared source length and the actual data length, causing hex2bin to write beyond the allocated heap buffer.
cve.now Index
- Exploitation0/40No signal
- Exposure17/25No login or user action needed, reachable over the network without a login · Unknown: Advisories don't say whether default setups are affected
- Reach10/20Shipped in major Linux distributions
- Severity9.1/10CVSS 8.1, total technical impact per CISA
- No patch5/5No patch listed yet
What would change the score
- Would score about 86 if added to CISA KEV
- Would score about 81 if CISA's SSVC rates exploitation active
- Would score about 46 if advisories confirm default setups are exposed
What to do
Workaround: Limit network access to the gdbserver port, for example with a firewall rule, because exposure is limited only by network access to that port. Stop gdbserver when it is not needed.
Timeline
- CVE published
- First seen by cve.now
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: total
- Record last updated
Affected versions
- crash
Version range not reported
- gdb
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- gdb
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- gdb
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- crash
Version range not reported
- gcc-toolset-14-gdb
Version range not reported
- gcc-toolset-15-gdb
Version range not reported
- gdb
Version range not reported
Show all 11 packagesShow fewer packages
- crash
Version range not reported
- gdb
Version range not reported
- gdb
Version range not reported
Evidence 2
- Report
- Link
Corrections
None so far.
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Questions about CVE-2026-121997
Is CVE-2026-121997 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
A heap buffer overflow in gdbserver's handler for the QTDPsrc packet lets a remote party reach native code execution in the gdbserver process, running as the user who started it. No authentication is required to send the packet.Source: access.redhat.com
Am I affected, and how do I check?
The flaw is in gdbserver as shipped with Red Hat Enterprise Linux 6, 7, 8, 9 and 10 and Red Hat Hardened Images. To check a system, look at the installed gdb package version (for example with rpm -q gdb) and whether gdbserver is running with a port reachable over the network.Source: access.redhat.com
How do I fix CVE-2026-121997?
The checked facts do not name a fixed package version, so no upgrade target can be given from them. Check the Red Hat advisory for the fixed gdb package for each product version.Source: access.redhat.com
What if there's no patch?
Limit network access to the gdbserver port, for example with a firewall rule, because exposure is limited only by network access to that port. Stop gdbserver when it is not needed.Source: access.redhat.com