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CVE-2025-34468

libcoap Stack-Based Buffer Overflow in Address Resolution DoS or Potential RCE

8.2 HighFix available

libcoap versions up to and including 4.3.5, prior to commit 30db3ea, contain a stack-based buffer overflow in address resolution when attacker-controlled hostname data is copied into a fixed 256-byte stack buffer without proper bounds checking. A remote attacker can trigger a crash and potentially achieve remote code execution depending on compiler options and runtime memory protections. Exploitation requires the proxy logic to be enabled (i.e., the proxy request handling code path in an application using libcoap).

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.75%Up 0.5 points since Jan 1, 2026
90%50%10%1%

What each source reports

CVE List Score used 8.2

libcoap Stack-Based Buffer Overflow in Address Resolution DoS or Potential RCE

libcoap versions up to and including 4.3.5, prior to commit 30db3ea, contain a stack-based buffer overflow in address resolution when attacker-controlled hostname data is copied into a fixed 256-byte stack buffer without proper bounds checking. A remote attacker can trigger a crash and potentially achieve remote code execution depending on compiler options and runtime memory protections. Exploitation requires the proxy logic to be enabled (i.e., the proxy request handling code path in an application using libcoap).

Record
CVE-2025-34468
CVSS 4.0
8.2 HighCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-121
Updated
2026-11-08
EUVDEUVD-2025-206064 8.2

libcoap versions up to and including 4.3.5, prior to commit 30db3ea, contain a stack-based buffer overflow in address resolution when attacker-controlled hostname data is copied into a fixed 256-byte stack buffer without proper bounds checking. A remote attacker can trigger a crash and potentially achieve remote code execution depending on compiler options and runtime memory protections. Exploitation requires the proxy logic to be enabled (i.e., the proxy request handling code path in an application using libcoap).

Record
EUVD-2025-206064
CVSS 4.0
8.2 HighCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-08
GitHub AdvisoriesGHSA-rj9f-6c28-qf6x 8.2

libcoap versions up to and including 4.3.5, prior to commit 30db3ea, contain a stack-based buffer...

libcoap versions up to and including 4.3.5, prior to commit 30db3ea, contain a stack-based buffer overflow in address resolution when attacker-controlled hostname data is copied into a fixed 256-byte stack buffer without proper bounds checking. A remote attacker can trigger a crash and potentially achieve remote code execution depending on compiler options and runtime memory protections. Exploitation requires the proxy logic to be enabled (i.e., the proxy request handling code path in an application using libcoap).

Record
GHSA-rj9f-6c28-qf6x
CVSS 4.0
8.2 HighCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-121, CWE-787
Updated
2026-11-02
NVD 8.2

libcoap versions up to and including 4.3.5, prior to commit 30db3ea, contain a stack-based buffer overflow in address resolution when attacker-controlled hostname data is copied into a fixed 256-byte stack buffer without proper bounds checking. A remote attacker can trigger a crash and potentially achieve remote code execution depending on compiler options and runtime memory protections. Exploitation requires the proxy logic to be enabled (i.e., the proxy request handling code path in an application using libcoap).

Record
CVE-2025-34468
CVSS 4.0
8.2 HighCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-121, CWE-787
Updated
2026-11-02
OSV 8.2

libcoap Stack-Based Buffer Overflow in Address Resolution DoS or Potential RCE

libcoap versions up to and including 4.3.5, prior to commit 30db3ea, contain a stack-based buffer overflow in address resolution when attacker-controlled hostname data is copied into a fixed 256-byte stack buffer without proper bounds checking. A remote attacker can trigger a crash and potentially achieve remote code execution depending on compiler options and runtime memory protections. Exploitation requires the proxy logic to be enabled (i.e., the proxy request handling code path in an application using libcoap).

Record
CVE-2025-34468
CVSS 4.0
8.2 HighCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-121
Updated
2026-11-02
OSVDEBIAN-CVE-2025-34468 9.8

libcoap versions up to and including 4.3.5, prior to commit 30db3ea, contain a stack-based buffer overflow in address resolution when attacker-controlled hostname data is copied into a fixed 256-byte stack buffer without proper bounds checking. A remote attacker can trigger a crash and potentially achieve remote code execution depending on compiler options and runtime memory protections. Exploitation requires the proxy logic to be enabled (i.e., the proxy request handling code path in an application using libcoap).

Record
DEBIAN-CVE-2025-34468
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2025-34468 8.2

libcoap versions up to and including 4.3.5, prior to commit 30db3ea, contain a stack-based buffer overflow in address resolution when attacker-controlled hostname data is copied into a fixed 256-byte stack buffer without proper bounds checking. A remote attacker can trigger a crash and potentially achieve remote code execution depending on compiler options and runtime memory protections. Exploitation requires the proxy logic to be enabled (i.e., the proxy request handling code path in an application using libcoap).

Record
UBUNTU-CVE-2025-34468
CVSS 4.0
8.2 HighCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
libcoap3
Debian:12
All versions, plus listed versions
4.3.1-14.3.1-24.3.3-14.3.4-14.3.4-1.1
Show 5 moreShow less
4.3.4-1.1~exp14.3.5-14.3.5-24.3.5-34.3.5-4
None known
libcoap3
Debian:13
before 4.3.4-1.1+deb13u3, plus listed versions
4.3.4-1.14.3.4-1.1+deb13u14.3.4-1.1+deb13u2
4.3.4-1.1+deb13u3
libcoap3
Debian:14
before 4.3.5-3, plus listed versions
4.3.4-1.14.3.5-14.3.5-2
4.3.5-3
libcoap
Ubuntu:18.04:LTS
All versions, plus listed versions
4.1.2-1
None known
libcoap2
Ubuntu:20.04:LTS
All versions, plus listed versions
4.2.0-24.2.1-1
None known
libcoap2
Ubuntu:22.04:LTS
All versions, plus listed versions
4.2.1-14.2.1-1build1
None known
libcoap3
Ubuntu:22.04:LTS
All versions, plus listed versions
4.3.0-24.3.0-2build1
None known
libcoap3
Ubuntu:24.04:LTS
All versions, plus listed versions
4.3.1-24.3.3-14.3.4-14.3.4-1.1build24.3.4-1.1build34.3.4-1.1build4
None known
libcoap3
Ubuntu:25.10
All versions, plus listed versions
4.3.4-1.1build4
None known
libcoap3
Ubuntu:26.10
All versions, plus listed versions
4.3.5-24.3.5-34.3.5-44.3.5-4ubuntu1
None known
libcoap3
Ubuntu:26.04:LTS
All versions, plus listed versions
4.3.4-1.1build44.3.5-14.3.5-2
None known

History

History
RecordedChangedSources
facts, referencesCVE List
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-34468 is a high vulnerability (CVSS 8.2) in Libcoap, published December 31, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.75%, the 55th percentile. Fixed in libcoap3 4.3.4-1.1+deb13u3.

References

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