VulnerabilityPublished 6 Jul 2026

CVE-2026-55079: V2 · Coder's unbounded memory allocation in provisioner file upload allows authenticated denial of service

Affects github.com/coder/coder/v2Source GCVE Database

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Not known to be exploited · CVSS 4.9 Medium : upgrade to 2.34.2 when convenient.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score

4.9Medium

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

EPSS: 0.6% chance of exploitation in 30 days – higher than 49% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.34.2, 2.33.8, 2.32.7 +1

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: High
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: High: The attacker is authorized with (i.e., requires) privileges that provide significant (e.g., administrative) control over the vulnerable component that could affect component-wide settings and files.
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 6 Jul 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 29 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 to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
Gogithub.com/coder/coder/v2	Affected >=2.34.0 <2.34.2	Fixed in 2.34.2
Gogithub.com/coder/coder/v2	Affected >=2.33.0 <2.33.8	Fixed in 2.33.8
Gogithub.com/coder/coder/v2	Affected >=2.30.0 <2.32.7	Fixed in 2.32.7
Gogithub.com/coder/coder/v2	Affected >=2.24.0 <2.29.17	Fixed in 2.29.17

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

AI-suggested

A fix is available and has been backported to all supported release lines: 2.34.2, 2.33.8, 2.32.7, and 2.29.17. Users should upgrade to these patched versions to remediate the vulnerability. As a workaround, restrict access to the provisioner daemon serve endpoint to trusted provisioner daemon service accounts to prevent unauthorized exploitation.

Description

### Summary `NewDataBuilder` in `provisionersdk/proto/dataupload.go` allocated a byte slice using the client-supplied `FileSize` from a `DataUpload` message without an upper-bound check. Although the DRPC wire limit is 4 MiB, the `FileSize` value itself was unconstrained ### Impact An authenticated user able to reach the provisioner daemon serve endpoint could send a roughly 50-byte message declaring a huge `FileSize` (for example 1 TiB), triggering an unrecoverable Go out-of-memory abort that terminates `coderd`. This is a single-message denial of service affecting the entire deployment. ### Patches The fix validates `FileSize` against an upper bound (`MaxFileSize = 100 MiB`) before allocation. The fix was backported to all supported release lines: | Release line | Patched version | |---|---| | 2.34 | [v2.34.2](https://github.com/coder/coder/releases/tag/v2.34.2) | | 2.33 | [v2.33.8](https://github.com/coder/coder/releases/tag/v2.33.8) | | 2.32 | [v2.32.7](https://github.com/coder/coder/releases/tag/v2.32.7) | | 2.29 (ESR) | [v2.29.17](https://github.com/coder/coder/releases/tag/v2.29.17) | ### Workarounds Restrict access to the provisioner daemon serve endpoint to trusted provisioner daemon service accounts. ### Resources - Fix: #25710 ### Credits Coder would like to thank Anthropic's Security Team (ANT-2026-22442) for independently disclosing this issue!

Impact

An authenticated user with access to the provisioner daemon serve endpoint can send a specially crafted DataUpload message with a large FileSize value, causing the provisioner daemon to allocate excessive memory. This triggers an out-of-memory abort in the Go runtime, terminating the coderd process and causing a denial of service affecting the entire deployment. There is no impact on confidentiality or integrity, only availability is affected.

Summary

The NewDataBuilder function in provisionersdk/proto/dataupload.go of github.com/coder/coder/v2 allocates a byte slice using the client-supplied FileSize from a DataUpload message without enforcing an upper bound. Although the DRPC wire protocol limits message size to 4 MiB, the FileSize field itself was unconstrained, allowing an authenticated user to specify an excessively large value (e.g., 1 TiB). This causes the provisioner daemon to allocate excessive memory, leading to an unrecoverable out-of-memory abort that terminates the coderd process, resulting in a denial of service for the entire deployment. The vulnerability is tracked as CVE-2026-55079 and CWE-789 (Uncontrolled Memory Allocation). Fixes validate FileSize against a 100 MiB maximum and have been backported to supported release lines including 2.34.2, 2.33.8, 2.32.7, and 2.29.17. Workarounds include restricting access to the provisioner daemon serve endpoint to trusted service accounts.

CWE-789Memory Allocation with Excessive Size Value (opens in a new tab)
Variant weakness
The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.
Implementation · Architecture and Design
Perform adequate input validation against any value that influences the amount of memory that is allocated. Define an appropriate strategy for handling requests that exceed the limit, and consider supporting a configuration option so that the administrator can extend the amount of memory to be used if necessary.
Operation
Run your program using system-provided resource limits for memory. This might still cause the program to crash or exit, but the impact to the rest of the system will be minimized.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
OWASP ASVS 4.0.3
V8.1.4 (opens in a new tab)
V13.4.1 (opens in a new tab)
V11.1.4 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 6 Jul 2026, 23:13 UTC

WeaknessesCWE-789

Technical details

References

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