VulnerabilityPublished 13 Aug 2026Updated 31 Oct 2026

CVE-2026-59884: Duplicity · pyasn1 BER/CER/DER decoder denial of service via unbounded long-form tag IDs

Affects duplicitySource GCVE Database

Compare

Not known to be exploited · CVSS 7.5 High : upgrade to 3.1.0_2 or 0.8.03 soon.

Data as of 1 Nov 2026, 02:06 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 3.1.0_2, 0.8.03

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 31 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade duplicity to 3.1.0_2 or 0.8.03.

Affected software

Product	Affected	Fixed in
Homebrewduplicity`pkg:brew/duplicity`Other threats	Affected >=0.7.06_1 <0.8.03 >=0.8.05_1 <3.1.0_2	Fixed in 0.8.03 3.1.0_2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch is available in pyasn1 versions 0.8.03 and 3.1.0_2 that limits long-form tag IDs to 20 octets and improves error handling. Users should upgrade to these fixed versions. As a workaround, applications can bound the size of untrusted input passed to the decode() function to prevent processing of oversized tag IDs.

Description

A denial of service vulnerability exists in the pyasn1 BER/CER/DER decoder used by Duplicity. The decoder processes long-form tag IDs without an upper bound, allowing crafted inputs to cause excessive CPU consumption or unhandled exceptions. This affects applications decoding untrusted BER/CER/DER inputs. The issue is fixed in versions 0.8.03 and 3.1.0_2 by limiting tag ID size and improving error handling.

Impact

This vulnerability allows denial of service by causing excessive CPU consumption when decoding maliciously crafted BER/CER/DER inputs. Additionally, on Python 3.11+, it may cause unhandled exceptions that bypass expected error handling, potentially destabilizing applications relying on pyasn1 for ASN.1 decoding.

Summary

The BER decoder in pyasn1, shared by CER and DER codecs, parses long-form tags by accumulating continuation octets in a loop without an upper bound on tag ID size. An attacker can craft input that forces the decoder to build an arbitrarily large integer, causing CPU usage to grow quadratically with input size, leading to denial of service. On Python 3.11 and later, oversized tag IDs can also trigger an unhandled ValueError during error message formatting, potentially bypassing caller error handling. Affected components include pyasn1.codec.ber.decoder, pyasn1.codec.cer.decoder, pyasn1.codec.der.decoder, and pyasn1.type.tag. The vulnerability is fixed in pyasn1 version 0.8.03 and 3.1.0_2 by limiting long-form tag IDs to 20 octets and hardening error handling.

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 1 Nov 2026, 02:06 UTC

Technical details

References

Community reviews

Related threats