Exim 4.88 before 4.99.4, in some proxy configurations, mishandles certain short payloads, leading to disclosure of uninitialized stack memory values to a client.
Weakness
The product checks a value to ensure that it is less than or equal to a maximum, but it does not also verify that the value is greater than or equal to the minimum.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Exim | Exim | 4.88 (including) | 4.99.4 (excluding) |
| Exim4 | Ubuntu | devel | * |
| Exim4 | Ubuntu | esm-infra-legacy/xenial | * |
| Exim4 | Ubuntu | esm-infra/bionic | * |
| Exim4 | Ubuntu | esm-infra/focal | * |
| Exim4 | Ubuntu | jammy | * |
| Exim4 | Ubuntu | noble | * |
| Exim4 | Ubuntu | questing | * |
| Exim4 | Ubuntu | resolute | * |
Extended Description
Some products use signed integers or floats even when their values are only expected to be positive or 0. An input validation check might assume that the value is positive, and only check for the maximum value. If the value is negative, but the code assumes that the value is positive, this can produce an error. The error may have security consequences if the negative value is used for memory allocation, array access, buffer access, etc. Ultimately, the error could lead to a buffer overflow or other type of memory corruption. The use of a negative number in a positive-only context could have security implications for other types of resources. For example, a shopping cart might check that the user is not requesting more than 10 items, but a request for -3 items could cause the application to calculate a negative price and credit the attacker’s account.