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CVE-2026-6986

Cesanta Mongoose GCM Authentication Tag tls_aes128.c mg_aes_gcm_decrypt signature verification

6.3 MediumFix available

A security vulnerability has been detected in Cesanta Mongoose up to 7.20. This issue affects the function mg_aes_gcm_decrypt of the file /src/tls_aes128.c of the component GCM Authentication Tag Handler. Such manipulation leads to improper verification of cryptographic signature. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is assessed as difficult. The exploit has been disclosed publicly and may be used. Upgrading to version 7.21 is capable of addressing this issue. It is advisable to upgrade the affected component. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
Low
Availability
None

Exploit likelihood

0.22%Up 0.2 points since Apr 26, 2026
90%50%10%1%

What each source reports

CVE List Score used 6.3

Cesanta Mongoose GCM Authentication Tag tls_aes128.c mg_aes_gcm_decrypt signature verification

A security vulnerability has been detected in Cesanta Mongoose up to 7.20. This issue affects the function mg_aes_gcm_decrypt of the file /src/tls_aes128.c of the component GCM Authentication Tag Handler. Such manipulation leads to improper verification of cryptographic signature. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is assessed as difficult. The exploit has been disclosed publicly and may be used. Upgrading to version 7.21 is capable of addressing this issue. It is advisable to upgrade the affected component. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.

Record
CVE-2026-6986
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C
CVSS 3.0
3.7 LowCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C
CVSS 2.0
2.6 AV:N/AC:H/Au:N/C:N/I:P/A:N/E:POC/RL:OF/RC:C
Weakness
CWE-347, CWE-345
Updated
2026-11-02
EUVDEUVD-2026-25662 6.3

A security vulnerability has been detected in Cesanta Mongoose up to 7.20. This issue affects the function mg_aes_gcm_decrypt of the file /src/tls_aes128.c of the component GCM Authentication Tag Handler. Such manipulation leads to improper verification of cryptographic signature. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is assessed as difficult. The exploit has been disclosed publicly and may be used. Upgrading to version 7.21 is capable of addressing this issue. It is advisable to upgrade the affected component. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.

Record
EUVD-2026-25662
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
Updated
2026-11-02
GitHub AdvisoriesGHSA-p5j9-fjff-qrmr 2.9

A security vulnerability has been detected in Cesanta Mongoose up to 7.20. This issue affects the...

A security vulnerability has been detected in Cesanta Mongoose up to 7.20. This issue affects the function mg_aes_gcm_decrypt of the file /src/tls_aes128.c of the component GCM Authentication Tag Handler. Such manipulation leads to improper verification of cryptographic signature. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is assessed as difficult. The exploit has been disclosed publicly and may be used. Upgrading to version 7.21 is capable of addressing this issue. It is advisable to upgrade the affected component. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.

Record
GHSA-p5j9-fjff-qrmr
CVSS 4.0
2.9 LowCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/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
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Weakness
CWE-345
Updated
2026-11-02
NVD 2.9

A security vulnerability has been detected in Cesanta Mongoose up to 7.20. This issue affects the function mg_aes_gcm_decrypt of the file /src/tls_aes128.c of the component GCM Authentication Tag Handler. Such manipulation leads to improper verification of cryptographic signature. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is assessed as difficult. The exploit has been disclosed publicly and may be used. Upgrading to version 7.21 is capable of addressing this issue. It is advisable to upgrade the affected component. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.

Record
CVE-2026-6986
CVSS 4.0
2.9 LowCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/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
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
CVSS 2.0
2.6 LowAV:N/AC:H/Au:N/C:N/I:P/A:N
Weakness
CWE-345, CWE-347
Updated
2026-11-02
OSV 2.9

Cesanta Mongoose GCM Authentication Tag tls_aes128.c mg_aes_gcm_decrypt signature verification

A security vulnerability has been detected in Cesanta Mongoose up to 7.20. This issue affects the function mg_aes_gcm_decrypt of the file /src/tls_aes128.c of the component GCM Authentication Tag Handler. Such manipulation leads to improper verification of cryptographic signature. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is assessed as difficult. The exploit has been disclosed publicly and may be used. Upgrading to version 7.21 is capable of addressing this issue. It is advisable to upgrade the affected component. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.

Record
CVE-2026-6986
CVSS 4.0
2.9 LowCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
Weakness
CWE-345, CWE-347
Updated
2026-11-02
OSVDEBIAN-CVE-2026-6986 2.9

A security vulnerability has been detected in Cesanta Mongoose up to 7.20. This issue affects the function mg_aes_gcm_decrypt of the file /src/tls_aes128.c of the component GCM Authentication Tag Handler. Such manipulation leads to improper verification of cryptographic signature. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is assessed as difficult. The exploit has been disclosed publicly and may be used. Upgrading to version 7.21 is capable of addressing this issue. It is advisable to upgrade the affected component. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.

Record
DEBIAN-CVE-2026-6986
CVSS 4.0
2.9 LowCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/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
Updated
2026-11-02
OSVJLSEC-2026-373 2.9

A security vulnerability has been detected in Cesanta Mongoose up to 7.20. This issue affects the function mg_aes_gcm_decrypt of the file /src/tls_aes128.c of the component GCM Authentication Tag Handler. Such manipulation leads to improper verification of cryptographic signature. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is assessed as difficult. The exploit has been disclosed publicly and may be used. Upgrading to version 7.21 is capable of addressing this issue. It is advisable to upgrade the affected component. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.

Record
JLSEC-2026-373
CVSS 4.0
2.9 LowCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/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 2.0
2.6 LowAV:N/AC:H/Au:N/C:N/I:P/A:N
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Updated
2026-11-02
OSVUBUNTU-CVE-2026-6986 2.9

A security vulnerability has been detected in Cesanta Mongoose up to 7.20. This issue affects the function mg_aes_gcm_decrypt of the file /src/tls_aes128.c of the component GCM Authentication Tag Handler. Such manipulation leads to improper verification of cryptographic signature. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is assessed as difficult. The exploit has been disclosed publicly and may be used. Upgrading to version 7.21 is capable of addressing this issue. It is advisable to upgrade the affected component. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.

Record
UBUNTU-CVE-2026-6986
CVSS 4.0
2.9 LowCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
CVSS 3.1
3.7 LowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
swupdate
Debian:12
All versions, plus listed versions
2022.12+dfsg-42022.12+dfsg-4+deb12u12022.12+dfsg-4+deb12u1~bpo11+12022.12+dfsg-4+deb12u22022.12+dfsg-4+deb12u3
Show 45 moreShow less
2023.05+dfsg-12023.05+dfsg-22023.05+dfsg-2~bpo12+12023.05+dfsg-32023.05+dfsg-42023.05+dfsg-52023.05+dfsg-5~bpo12+12023.12+dfsg-12023.12+dfsg-1~bpo12+12023.12.1+dfsg-12023.12.1+dfsg-1~bpo12+12023.12.1+dfsg-22023.12.1+dfsg-2~bpo12+12024.05+dfsg-12024.05.2+dfsg-12024.05.2+dfsg-22024.05.2+dfsg-2~bpo12+12024.12+dfsg-12024.12+dfsg-22024.12+dfsg-2~bpo12+12024.12.1+dfsg-12024.12.1+dfsg-1~bpo12+12024.12.1+dfsg-22024.12.1+dfsg-32024.12.1+dfsg-3~bpo12+12025.05+dfsg-12025.05+dfsg-22025.05+dfsg-2~bpo13+12025.05+dfsg-32025.05+dfsg-3~bpo13+12025.12+dfsg-12025.12+dfsg-102025.12+dfsg-10~bpo13+12025.12+dfsg-10~bpo13+22025.12+dfsg-22025.12+dfsg-2~bpo13+12025.12+dfsg-32025.12+dfsg-42025.12+dfsg-52025.12+dfsg-62025.12+dfsg-72025.12+dfsg-7~bpo13+12025.12+dfsg-82025.12+dfsg-92026.05+dfsg-1
None known
swupdate
Debian:13
All versions, plus listed versions
2024.12.1+dfsg-32024.12.1+dfsg-3+deb13u12024.12.1+dfsg-3+deb13u22025.05+dfsg-12025.05+dfsg-2
Show 27 moreShow less
2025.05+dfsg-2~bpo13+12025.05+dfsg-32025.05+dfsg-3~bpo13+12025.12+dfsg-12025.12+dfsg-102025.12+dfsg-10~bpo13+12025.12+dfsg-10~bpo13+22025.12+dfsg-22025.12+dfsg-2~bpo13+12025.12+dfsg-32025.12+dfsg-42025.12+dfsg-52025.12+dfsg-62025.12+dfsg-72025.12+dfsg-7~bpo13+12025.12+dfsg-82025.12+dfsg-92026.05+dfsg-12026.05+dfsg-22026.05+dfsg-32026.05+dfsg-3~bpo13+12026.05+dfsg-42026.05.1+dfsg-12026.05.1+dfsg-1~bpo13+12026.05.1+git20261001+dfsg-12026.05.1+git20261001+dfsg-22026.05.1+git20261001+dfsg-2~bpo13+1
None known
swupdate
Debian:14
before 2025.12+dfsg-10, plus listed versions
2024.12.1+dfsg-32025.05+dfsg-12025.05+dfsg-22025.05+dfsg-2~bpo13+12025.05+dfsg-3
Show 14 moreShow less
2025.05+dfsg-3~bpo13+12025.12+dfsg-12025.12+dfsg-10~bpo13+12025.12+dfsg-10~bpo13+22025.12+dfsg-22025.12+dfsg-2~bpo13+12025.12+dfsg-32025.12+dfsg-42025.12+dfsg-52025.12+dfsg-62025.12+dfsg-72025.12+dfsg-7~bpo13+12025.12+dfsg-82025.12+dfsg-9
2025.12+dfsg-10
Mongoose_jll
Julia
before 7.21.0+0
7.21.0+0
swupdate
Ubuntu:22.04:LTS
All versions, plus listed versions
2020.11-22021.04-1.12021.04-22021.04-2build12021.11-1
None known
swupdate
Ubuntu:24.04:LTS
All versions, plus listed versions
2023.05+dfsg-32023.05+dfsg-42023.05+dfsg-4build12023.05+dfsg-52023.12+dfsg-12023.12.1+dfsg-1ubuntu12023.12.1+dfsg-1ubuntu42023.12.1+dfsg-1ubuntu5
None known
swupdate
Ubuntu:25.10
All versions, plus listed versions
2024.12.1+dfsg-1build22024.12.1+dfsg-22024.12.1+dfsg-32025.05+dfsg-2ubuntu1
None known
swupdate
Ubuntu:26.10
All versions, plus listed versions
2025.12+dfsg-4ubuntu12026.05+dfsg-3ubuntu22026.05+dfsg-4ubuntu12026.05.1+dfsg-1ubuntu12026.05.1+git20261001+dfsg-1ubuntu1
None known
swupdate
Ubuntu:26.04:LTS
All versions, plus listed versions
2025.05+dfsg-2ubuntu12025.05+dfsg-3ubuntu12025.12+dfsg-1ubuntu12025.12+dfsg-2ubuntu12025.12+dfsg-3ubuntu12025.12+dfsg-4ubuntu1
None known

History

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

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

In short

CVE-2026-6986 is a medium vulnerability (CVSS 6.3) in Automattic Mongoose, published April 25, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.22%, the 12th percentile. Fixed in swupdate 2025.12+dfsg-10.

References

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